Mode NDB

NDB: the Morse identification of a long-wave navigation beacon.

Group	Aviation
Default frequency	0.35 MHz
Default sample rate	256 ksps
In the mode list	Ident, 190-535 kHz

Step-by-step: Tutorial-NDB

What NDB is

Non-directional beacons are long-wave radio beacons, usually between 190 and 535 kHz (some sit higher), used for navigation. Each sends its identification in Morse code at about 7 words per minute.

Frequencies and settings

Setting	Value
Start frequency	0.35 MHz
Tuning range of the mode table	0.19 to 0.535 MHz
Sample rate asked	256 ksps
Lowest working rate	48 ksps
Channel width	10 kHz

OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is Ident, 190-535 kHz.

What OnAir shows

NDB (non-directional beacon) on long wave, 190-535 kHz: the Morse ident of an aeronautical beacon (a keyed 400 Hz or 1020 Hz tone, or a keyed carrier, about 7 WPM). Receive only. Not the HF beacon list.

Tips and caveats

• Checked with generated signals and impairments; recordings of real signals welcome.
• Which radio: Only in direct-sampling mode, which OnAir offers in the radio settings, and the signal may be weak or absent. SDRplay and Airspy HF+ radios reach low frequencies directly.
• Try it without a radio: most modes include a built-in synthetic test signal, so you can open the screen and try the controls first.
• Receiving and the law: Receiving aircraft broadcasts is legal in many countries, but some restrict listening to or using what you hear. OnAir is a receiver. Check the rules where you live. See Legal.

Related pages

• All modes, Aviation
• Supported radios, Troubleshooting, FAQ
• More in Aviation: ADS-B, Mode S uplink, ACARS, VDL2, VDL4, HFDL, Airband, VOR, ILS, Drone Remote ID, UAT, FLARM, DJI drones